21212221001 has 4 divisors (see below), whose sum is σ = 21230461392. Its totient is φ = 21193980612.

The previous prime is 21212220949. The next prime is 21212221007. The reversal of 21212221001 is 10012221212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21212221001 - 2¹⁸ = 21211958857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212221007) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9118451 + ... + 9120776.

It is an arithmetic number, because the mean of its divisors is an integer number (5307615348).

Almost surely, 2^21212221001 is an apocalyptic number.

It is an amenable number.

21212221001 is a deficient number, since it is larger than the sum of its proper divisors (18240391).

21212221001 is a wasteful number, since it uses less digits than its factorization.

21212221001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18240390.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21212221001 its reverse (10012221212), we get a palindrome (31224442213).

The spelling of 21212221001 in words is "twenty-one billion, two hundred twelve million, two hundred twenty-one thousand, one".